Some education if someone has the time, please

Discussion in 'Subaru' started by geosnooker2000, Apr 3, 2019.

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  1. Apr 4, 2019 #21

    Dana

    Dana

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    I've wondered about that. If you have the reduced (25 vs. 40 hours) phase 1 test time because you used a certificated engine/propeller combination, are you then obligated to follow all manufacturer's guidelines and ADs to maintain that engine's certificated status?

    When I bought my plane, the Lycoming data plate for the engine in my plane... was in an envelope with the logbooks.
     
  2. Apr 4, 2019 #22

    proppastie

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    Depending on the engine at tbo you probably get 500 to 1000 more hours. A65 is bullet-proof

    Might want to learn to fly first though. Outlook might change.
     
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  3. Apr 4, 2019 #23

    TFF

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    The engine companies want the tags removed, the FAA wishes the tags on for data if crashed. It voids the certification once on a homebuilt until a conformity inspection is done by an A&P and written in the logs. A friend with his first RV found a used certified Lycoming and it required 25 hrs to fly off. The second one he built and splurged for a new Lycoming but it was the one Vans specs out, 40 hr fly off because it was not a certified engine by the data tag. Once on a homebuilt, you can do anything you want and fly it for as long as you want. There is no required TBO. Only essentially certificated operations like airlines have to follow TBOs; only a few exceptions.
     
  4. Apr 4, 2019 #24

    Toobuilder

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    Nope. The 25 hour thing is an option at the time of initial AWC. There is generally no requirement to maintain that initial configuration beyond the initial inspection.
     
  5. Apr 6, 2019 #25

    geosnooker2000

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    Thank you for the information! This is why I came here.
     
  6. Apr 6, 2019 #26

    geosnooker2000

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    Okay... Give me an example of something that I would have to MACHINE. Not fabricate, but machine. As I said in a previous post, I have been down to the block on my daily driver (successfully, I might add), so I don't know how much of a "serious background in engines" you're talking about, but I'm not without some practical experience. Is it your position that only professional engine mechanics can put together a firewall-forward design?

    And I might add... since this is my thread... that a lot of the responses I have gotten (here AND elsewhere) have revolved around "time" and "trouble" and "efficiency". Well, I'm here to learn about Subaru Auto conversions. I see that they exist, so they are possible. I may, at the end of my studies decide I would rather go the Rotax route, but I'm in a Subaru sub-forum. I would have thought that I would have found a lot more enthusiasm.
    Let me point out that, to all of you talking about cost, all we hear and read in the kitplanes-type articles about auto-conversions is the cost savings. I mean, that's the whole point, right? If a piston breaks, a head cracks, a pretty valve cover gets scuffed, what is the cost difference in a Lycoming part and a Subaru part? Right? Am I wrong about that? Have I got it all wrong?

    People, I am not trying to build my airplane in the next 6 months. I probably won't even start for 6 months. More like a year. I'm doing the responsible thing. I'm doing my research well before I start my project. And all I want to know here is, what are the individual items it takes besides the engine (and a PSRU) etc. to have a Subaru power my plane. I didn't come here for a bunch of "aww, you don't want to get into that, it's too complicated"

    Sorry to sound so reactionary. Not directed at any one person. Just please try and be helpful, not discouraging.
     
  7. Apr 6, 2019 #27

    BJC

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    I’m not “an engine guy” but I have watched friends who thought that they were have problems with Subaru conversions. Ultimately, they each went the Lycoming route, and would have have had less time and money in the FWF package had they started with the Lycoming or a clone. When considering the cost of a failed part, one must also consider the cost of potential airframe repairs that resulted from an off-airport landing. Depending on multiple factors, that could be much more expensive than an entire engine.

    None of the above is intended to disparage the Subaru or other conversion FWF packages. (And it is the entire FWF package, not just the engine.) There are many examples of successful Subaru installations. Ross has a successful installation, and can point to many others.

    My suggestion is: if you want to go flying in a homebuilt, use an aircraft engine or a proven clone; it you enjoy tinkering with engines, have the skills and knowledge, or want to develop them, and want to have the advantages (to some) of an auto engine, do so.

    BTW, not all the vendors have treated their customers the way that they should have.


    BJC
     
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  8. Apr 6, 2019 #28

    Dana

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    OK, an overview:

    There have been few really successful auto conversions. Most of the successful ones are VW, Corvair, and Subaru, note that they already look like airplane engines (4 or 6 cylinder flat opposed). The VW is the most successful, not only because it's been around for a long time, but it's very simple and air cooled. Subaru, you have more to deal with.

    Automobile and aircraft engines are designed for very different duty cycles. A car engine may reach its rated HP output intermittently and briefly during acceleration, or pulling up a long hill. An aircraft engine, OTOH, will run at full power for 5-10 minutes (takeoff and climb), then cruise at 75-80% power for hours. So cooling becomes a huge factor... I'm not familiar with Subaru conversions but cooling is the limiting factor on VW conversions, which is why they top out well under 100HP. RPM is also a factor, auto engines are designed to produce their HP at a much higher rpm than is efficient for a propeller, so you need a redrive or you take the hit on propeller efficiency.

    Electronic engine controls are also another factor; in cars they're designed around a the car's duty cycle and optimized for reduced emissions (for example turning on the check engine light if the catalytic converter fails, but you won't have a cat on a plane). They often include a reduced power "limp mode" to get you home if something fails, but in an airplane that reduced power might be just enough to get you to the scene of the crash.

    Car engine parts are cheaper-- often a lot cheaper-- but a BJC pointed out above you have to consider the total cost of a failure, when you can't just pull over to the side of the road and fix it, or wait for a tow truck. When I flew my half VW powered plane, I was always looking for a place to land, expecting the engine to quit at any time (it never did, completely).

    So what do you have to do or make? As I said, I'm not familiar with the specifics of Subarus in airplanes, but in general, you'll probably need to:
    • Make or buy and install an output pulley for the reduction drive
    • Make or buy an exhaust system to suit the airplane
    • Install a simplified ECU, or convert to carburetor
    • If you remove the stock ECU and go carburetor, install a new ignition system
    • Make and install plugs or covers for removed sensors, etc.
    • Make an engine mount
    • Make or buy a reduction drive-- a biggie, not nearly as simple as it looks, torsional vibration is the bane of redrives, sometimes you get lucky and sometimes you don't without some serious engineering effort.
    • You may have to move (and fabricate brackets for) accessories like the alternator
    • Design and fabricate a new cooling system (radiator, hoses, etc.) to suit the aircraft installation
    • Design and fabricate the cowling and ducting to direct air around the engine, not as simple as just hanging a radiator on the front of a car
    If I was looking at auto conversions for the reduced cost, a VW would be the only choice, it's the only one with the established history and knowledge base to know it'll be reliable... but it still won't be as reliable as a Continental or Lycoming, and will require more attention during its lifetime. Any of the others, including Subaru, should be contemplated only if you go into it as an experimental project, and expect to (and enjoy!) spend a lot of extra time working on it both during the build and on an ongoing basis after it's flying, working out how to solve problems (there's a big difference between mechanicing an existing design and engineering something something new). Not to say that you shouldn't do it, but do it for the right reasons and know what you're getting into.
     
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  9. Apr 6, 2019 #29

    blane.c

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    Experimental engines are the perfect place for multiple engines. If you don't entirely trust one of them, you may as well not trust several of them. If one of them rewards your mistrust maybe the others will see you home.
     
  10. Apr 6, 2019 #30

    rv6ejguy

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    Research is good. It can save a lot of time and heartbreak down the road before you start your project.

    If you look at my RV6A project pages, you'll see plenty of parts which I had to machine. Yes, you can farm those out of course. You'll be doing a lot of welding as you can see in my engine mount page.

    Yes, my position is that without a solid and extensive engine, mechanical, fabrication type background, you won't be successful in building your own auto conversion. I've seen way more fail at it than succeed, even from some MEs and experienced engine guys. There are lots of things that can and will bite you along the way.

    The $ cost may be lower with an auto conversion (mine was) but the time spent will be much higher. After you complete the airframe build, will you have the gumption left to start on the engine part which is another huge task in itself?

    In the end though, an EJ Subaru will be way too heavy for the Sling so if you are going to build that aircraft and do an auto conversion, you'll have to look at a lighter engine. I suggest looking at the Aeromomentum packages where a lot of the work with the fuel system and redrive is already handled for you.
     
  11. Apr 6, 2019 #31

    Toobuilder

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    Geo- what is your primary objective? Is it to fly or tinker?

    If it looks like the membership is "negative", it is just to give you a dose of reality and perhaps test your resolve. I think most here are supportive of auto conversions as a concept but if the goal is to provide "inexpensive" power for your airplane - the odds are stacked against you. Despite manufacturers claims, there really is no cookbook based plan to hang a Subie on your airplane like there is for an established aircraft engine. There is a LOT more than simply swinging a propeller. You are on your own for fuel, cooling, torsional vibration, structure, and aerodynamics.

    And considering your own admittedly modest experience, I think most of us are seeing red flags. Not because we are looking down on you, but because we see an opportunity to capture another homebuilt enthusiast and we don't want that passion to expire on a long, arduous journey like an auto conversion.

    So if the primary consideration is to learn, then you have a very long road ahead. I think most of us will be supportive, but you better have your eyes wide open going in. You will not be zipping around the sky anytime soon.
     
  12. Apr 6, 2019 #32

    blane.c

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    Finding a airplane, polishing it, tinkering on it, finding a significant other that will live in the hanger with you and help you polish the airplane. All are rewarding accomplishments. Oh yes I forgot, flying the airplane, ahh that is the sweet spot. Then you get to polish it again. For some reason people on this forum want the added joy of building it or even designing it and then building it. The heart wants what the heart wants.
     
  13. Apr 6, 2019 #33

    geosnooker2000

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    Thank you for the thoughtful post. I would agree with the VW being the choice, but I'm not going to try and fly a 4 seat plane behind a100hp or less engine. I'm looking for 140hp, minimum. That is why I'm looking at the Subaru as an option. It is the right hp range by all accounts.
     
  14. Apr 6, 2019 #34

    mcrae0104

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    GS- just go fly. Don't worry about the Sling or the right engine for right now. Your opinions will evolve after you're flying, and if they stay the same you haven't lost anything.
     
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  15. Apr 6, 2019 #35

    BBerson

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    Dick Vangrunsven learned much and tested his design skills first with a one seater. Can't kill a passenger if one seat. Think about the responsibility involved as pilot in command when with a passenger that trusts the pilot and with no knowledge of risks.
    I don't think Van ever considered an auto engine.
     
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  16. Apr 6, 2019 #36

    blane.c

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  17. Apr 6, 2019 #37

    blane.c

    blane.c

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    I used to take up my friends in my experimental cubby. They would see the big experimental sign and ask "what's experimental about it" and I'd reply "everthing".
     
  18. Apr 6, 2019 #38

    BBerson

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    I doubt you had anything truly experimental like a PSRU in your Cubby.
     
  19. Apr 6, 2019 #39

    blane.c

    blane.c

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    Engine was O-290-D2 with a 82" McCauley Borer prop 42" pitch. Twice the fuel capacity as standard Super Cub 72gallons but no header tank. Atlee Dodge brace in skylight area. Atlee Dodge heavy duty gear and 30" floatation tires with air stem in sidewall (were it belongs on a bush plane) and disc brakes. 900lbs empty. PA-11 fuselage (top deck cut out and Super Cub top deck welded in) 1st year no flap Super Cub wings with 14 inch long spoilers added (so you could get rid of excess lift when necessary). Atlee Dodge cross brace in empennage, extended baggage and custom door access. Skiis in winter. PA-11 horizontal stabilizer (a lot less surface than a Super Cub) so the tail dropped 1st, like dragging a hook. And stuff.
     
  20. Apr 6, 2019 #40

    TFF

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    That is not do much experimental as picking the best bits of a certified line of planes. Even using certified stc stuff.
     

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